1. Technical Field
The present invention relates to orthopedic therapy and in particular to devices that provide dynamic measurable therapy for use by orthopedic patients. More particularly, the present invention relates to a physical therapy system and device that can be manually operated by a post-operative patient without the need of professional on site assistance, wherein the degree of movement of the limb or joint of interest is measured and recorded so as to provide a record of the progress of the prescribed post-operative therapy for immediate feedback to the patient as well as for long term data recordation for the therapist or physician.
2. Background Art
The success of joint reconstructive or replacement surgery depends largely upon the postoperative rehabilitation process. This is particularly true for a total knee arthroplasty. In total knee arthroplasty surgeons are typically able to achieve a great, range of joint motion for the sedated patient on the operating table. However, the quantity and quality of the post-operative therapy is critical to the patient's ultimate range of motion and therefore, the ultimate success of the surgical procedure. A limited range of motion of a post-operative joint, particularly a knee, will result in pain and limited function. It is generally understood that there is a six-week window of opportunity after surgery during which a patient can, through therapy and exercise, maximize his ultimate range of motion for the post-operative joint. Very important to the success of any post-operative therapy is the patient's commitment to maximizing the effort to rehabilitate the affected joint. Conventional post-operative therapies necessarily have to enlist the patient's commitment to and compliance with the prescribed regime as much as possible. However, the success of the postoperative therapy in large part relies more on the therapist contribution than on passive mechanized therapy devices that may or may not be properly, routinely, and adequately employed by the patient.
Continuous passive motion (CPM) machines and/or manually applied physical therapy to an injured or post operative limb are the primary rehabilitation treatments chosen by most doctors and therapists. Many limb and joint exercising devices are known. Generally, these machines have a motor driven limb support with the limb support capable of being set to periodically move the limb in a preset range of positions for a preset length of time and at a preset speed. Once these parameters have been selected the machine automatically moves the limb from a straightened position back and forth to these pre-selected positions at the pre-selected speeds and durations.
One major drawback to these motor driven machines is the problem of selecting the optimum settings for the machine. While resetting positions and safety cut-off switches are usually provided for the user, the initial settings for the machines, which are set by the therapist, are frequently too severe and painful. Later, as the therapy progresses and the joint becomes more limber and capable of greater movement the settings are often insufficient and therefore less helpful in taking the rehabilitation as far as possible.
Further, conventional therapy machines and therapists cannot sense the level of pain experienced by the patient during movement of the joint or the true degree of stiffness of the joint. For this reason, the rehabilitative therapy provided to the patient may be too severe or too reserve. Only the patient is truly aware of what joint motion limits he is capable of reaching on any given day of the rehabilitative period.
A conventional rehabilitative therapy regime for a post-operative total knee replacement would include both the use of a therapist and a continuous passive motion (CPM) machine. In use, the patient would lie down and securely strap his knee into the machine. The machine with its preset motion, speed, and duration parameters would be turned on while the patient passively endured the machine bending the knee to a prescribed range of motion. The range of motion can be adjusted by the therapist to a level he believes to be within the patient's pain and motion tolerance; however the level of uncertainty of the optimum settings for any given patient is high. The CPM is typically prescribed for self-use at home by the patient for a period of several weeks after surgery. During this rehabilitative period the involvement of a physical therapist in providing manipulative therapy and in monitoring the use of the CPM is generally considered the most important element in a successful rehabilitation regime. Even if the settings on the CPM are relatively appropriate for the patient, it remains that the effectiveness of the CPM in the rehabilitative regime is totally dependent upon the amount of effective use it receives. The physical therapist working with the postoperative patient can improve the rehabilitation progress by monitoring the patient's use of the CPM and by passively stretching the patient's knee and recording the progress; however this spot-checking of the patient's use of the CPM is at best periodic and isolated and not necessarily a true picture of whether or not the patient is making good use of the machine. Further, inconvenience, forgetfulness, pain avoidance and many other reasons can contribute to the patient's neglect of his prescribed CPM and home therapy regime. For this reason, the therapist's sessions with the patient are often the most effective part of the rehabilitative effort. Unfortunately, the patient's sessions with the therapist will, at best, be limited to about 45 minutes for each of two or three sessions per week for six weeks. Over the six week long post-operative period the therapist will likely spend no more than 13 to 15 hours working with the patient. For this reason, a good therapist will typically prescribe a variety of additional exercises to assist the patient in the effort of stretching the knee into flexion and extension during those long periods when the patient is at home without the benefit of the therapist presence. For example, extension of the knee joint is often augmented by having the patient prop an object under his heel after which the patient will press the knee downward from above. Flexion exercises are more difficult. Efforts to improve flexion of the knee can be augmented by the patient sitting on a chair and pulling the operative leg back with the opposite leg. While these and other self-help exercises can be useful, they are only beneficial if the patient exercises a great deal of self-discipline and strictly adheres to the prescribed program. The patient is typically left alone to exercise or to neglect his prescribed therapy program for the majority of those initial few weeks when a therapy program can be most effective. Further, although the time during which the therapist is actively involved in sessions with the patient is of great value, it remains that providing such professional assistance is becoming increasingly expensive for the patient and his insurance company. Limited finances or insurance can curtail or abruptly end the active assistance of a professional therapist. For this reason, it is very important that, within reasonable cost constraints, the best possible tools be provided to aid the patient in the self-administered portion of the exercise program.
Another important aspect of the patient's rehabilitation program is the requirement to accurately measure and report the degree of flexion and extension of the joint in a timely manner. It is very important that the therapist and the surgeon are aware of the progress being made by the patient in order to permit course corrections in the therapy program as needed. At present, the degree of flexion or extension of a joint is measured by the therapist using a goniometer, an angle finder, which the therapist holds on the side of the patient's knee and uses his best-guess to align the device with the leg. The therapist generally uses this conventional angle measurement technique intermittently to determine the level of progress in the rehabilitative effort being made by the patient. Studies presented at the Orthopedic Trauma Association (OTA) 2000 meeting indicated that a visual inspection and angle estimation of a joint by an attending surgeon, an orthopedic fellow, and an orthopedic senior resident varied from the actual angle of the joint as determined by radiological examination by an average of 6.5° and the difference between the goniometer measurement and the radiologically determined angle was only slightly better at 5.6°. In addition, a significant difference in 1 of 8 comparisons among attending surgeons, fellows and residents was found (Poster No. 82, OTA 2000 Posters). Further, the inaccuracy of visual or goniometer estimates of a joint angle can also be attributable to the obvious possibility that the therapists estimate of proper alignment of the goniometer to the patient's leg can vary considerably from one visit to the next; what seems like progress from an earlier session may only be the result of inaccurate instrument alignment at a subsequent session. This is particularly true when a substitute therapist must attend to the patient. In such cases an inconsistent alignment of the goniometer should be expected and therefore the recorded progress would be expected to be erroneous.
To date there has been no therapy system provided that effectively enables the patient to completely control all parameters of his rehabilitative machine exercise therapy so as to actively stretch the knee joint with immediate biofeedback as well as precise recordation of therapy progress. Further, the accuracy of any recordation of the level of progress using conventional measurement techniques and devices is at best questionable. What is needed is a joint rehabilitative therapy system that allows the patient alone to conveniently use the device on a daily basis wherein the parameters of the degree of extension and flexion, speed, and duration are established by the patient using a real time biofeedback mechanism and allowing the patient to limit or extend the effort to conform to his pain threshold rather to that which a therapist has applied a best-guess.